Filters are used daily to remove constituents from a variety of fluids. Filter usage varies in scale and the nature of the application. For example, filters may be used in an automobile to remove undesired constituents from the fuel before the constituents damage the engine. Filters may be used by industry to recover a desired constituent from a fluid stream, such as the filtration of a process stream to recover an expensive catalyst. In addition, a fluid may be filtered to remove more than just one constituent. In such case, a filter with multiple stages or with multiple filter media, each capable of removing a different constituent, may be employed.
Filters are also used in the treatment of water intended for human consumption and use, where the water is expected to be either free of harmful constituents or contain concentrations of such constituents that are below harmful levels. To provide water for use in homes and businesses, municipalities may utilize industrial scale processes in an effort to eliminate or reduce harmful constituents present in water drawn from large, naturally occurring water sources. Water is also frequently obtained on a smaller scale from wells and springs and usually without any treatment prior to consumption.
Unfortunately, the cleanliness of a particular water supply is sometimes questionable. The consistency and efficiency of treatment by municipalities may vary due to numerous factors such as heavy rainfall, equipment failures, and usage levels. Depending upon the seriousness of a variation in treatment, a municipality may be forced to notify its users that further treatment of the water supplied, e.g. boiling, is required at the point-of-use before consumption or use is safe. Water obtained directly from a natural source may also become suspect depending upon environmental conditions near the source. Wells and springs can become contaminated due to rain water run-off washing a contaminant into the source.
Various fluid filtration devices have been developed. For example, in the area of water filtration, devices range from those located at the point-of-use (e.g. the spigot of a kitchen sink, gravity-flow dispensers such as water pitchers, and low-pressure dispensers such as sports bottles) to the generally bulkier point-of-entry units hidden from view within the plumbing of a home or office.
Current filtration devices may require a large pressure drop or residence time to operate effectively. For example, current industrial filters may require that the pressure of the unfiltered fluid supplied to the filter be at a certain level before the filter will produce filtered fluid at a rate that is practical. Similarly, current water filtration devices may require either a source of unfiltered water above an operable minimum pressure, or may require a lengthy residence time for the unfiltered water to flow through the filter.
Filters with a large pressure drop may be more expensive to use because of the energy required to pressurize the unfiltered fluid or because of the time spent during the filtration process. In addition, filters with a large pressure drop may cause the system in which they are installed to function improperly or less efficiently. For gravity flow systems, a large pressure drop filter may be inoperable under current technology. The installation of additional equipment or modifications of the existing system may be necessary to circumvent the pressure drop problem.
For example, point-of-use water filtration systems exist for installation with a conventional sink. These systems are generally installed under the sink or at the end of the faucet. Such systems may occupy space normally used for storage or, in the case of installations at the faucet end, may consume space needed while using the sink for cleaning, food preparation, and the like. Many conventional sinks include a water sprayer and installation of a filter into the sprayer could result in a savings of space. However, depending upon the pressure of water supplied to the sink, the water sprayer may not operate properly if a filter is used in conjunction with the water sprayer.
The faucet assembly of a conventional sink typically includes a shuttle valve within the assembly. When the water sprayer is activated, the shuttle valve operates by water pressure to direct water flow away from the faucet and to the water sprayer. However, if a water filter requiring a large pressure drop is added to the sprayer or the flexible conduit generally connecting the water sprayer to the faucet assembly, the shuttle valve may not operate to direct flow to the sprayer.
Therefore, a need exists for a fluid filter that may remove constituents from a fluid stream. More specifically, there exists a need for a fluid filter that may remove constituents from a fluid stream while occupying a minimum of space. Even more desirably, there exists a need for a fluid filter that also minimizes the pressure drop incurred during the filtration process.